Driving circuit and optical module

Abstract

A driving circuit includes a first transistor that includes a first terminal, a second terminal, and a third terminal; a second transistor having a fourth terminal, a fifth terminal, and a sixth terminal; and an output portion that outputs a signal between the second transistor and a second current source to a light emitting element, wherein the first terminal is coupled to a first power source, a signal is input to the second terminal, and the third terminal is grounded through a first current source which is different from the second current source, and the fourth terminal is coupled to a second power source which is the same as or different from the first power source via the second current source, the fifth terminal is coupled to a voltage source or a bias circuit, and the sixth terminal is coupled between the first transistor and the first current source.

What is claimed is: 
     
       1. A driving circuit comprising:
 a first transistor that includes a first terminal as a collector, a second terminal as a base, and a third terminal as an emitter; 
 a second transistor having a fourth terminal as a collector, a fifth terminal as a base, and a sixth terminal as an emitter; and 
 an output portion that outputs a signal between the second transistor and a second current source to a light emitting element, wherein 
 the first terminal is coupled to a first power source, a signal is input to the second terminal, and the third terminal is grounded through a first current source which is different from the second current source, and 
 the fourth terminal is coupled to a second power source which is the same as or different from the first power source via the second current source, the fifth terminal is coupled to a voltage source or a bias circuit, and the sixth terminal is coupled between the first transistor and the first current source. 
 
     
     
       2. The driving circuit according to  claim 1 ,
 wherein the driving circuit is a single end-type driving circuit. 
 
     
     
       3. The driving circuit according to  claim 1 ,
 wherein the fifth terminal of the second transistor is coupled to the bias circuit that supplies a bias voltage in accordance with a voltage of the first power source. 
 
     
     
       4. The driving circuit according to  claim 3 , further including
 a differential amplifier circuit that differentially amplifies the signal which is input to the second terminal of the first transistor by the first power source at a previous stage relative to the first transistor, 
 wherein the bias circuit generates the bias voltage by adding a positive-phase signal and a negative-phase signal obtained by differential amplification by the differential amplifier circuit. 
 
     
     
       5. The driving circuit according to  claim 1 , further including:
 a differential amplifier circuit that differentially amplifies the signal which is input to the second terminal of the first transistor by the first power source at a previous stage relative to the first transistor; and 
 an extraction circuit that extracts a high-frequency component of a signal obtained by differential amplification by the differential amplifier circuit and supplies the extracted high-frequency component to the fifth terminal of the second transistor. 
 
     
     
       6. The driving circuit according to  claim 5 , further including
 an inductor one terminal of which is coupled to the voltage source or the bias circuit coupled to the fifth terminal of the second transistor and the other terminal of which is coupled to between the extraction circuit and the fifth terminal of the second transistor. 
 
     
     
       7. The driving circuit according to  claim 5 
 wherein a positive-phase signal out of the positive-phase signal and a negative-phase signal obtained by the differential amplification of the differential amplifier circuit is input to the second terminal of the first transistor, and 
 the extraction circuit extracts the high-frequency component from the negative-phase signal. 
 
     
     
       8. An optical module comprising:
 a first transistor that includes a first terminal as a collector, a second terminal as a base, and a third terminal as an emitter; 
 a second transistor having a fourth terminal as a collector, a fifth terminal as a base, and a sixth terminal as an emitter; and 
 a light emitting element that emits light in accordance with a signal between the second transistor and a second current source, wherein 
 the first terminal is coupled to a first power source, a signal is input to the second terminal, and the third terminal is grounded through a first current source which is different from the second current source, and 
 the fourth terminal is coupled to a second power source which is the same as or different from the first power source via the second current source, the fifth terminal is coupled to a voltage source or a bias circuit, and the sixth terminal is coupled between the first transistor and the first current source. 
 
     
     
       9. A driving circuit comprising:
 a first transistor having a first terminal as a drain, a second terminal as a gate, and a third terminal as a source; 
 a second transistor having a fourth terminal as a drain, a fifth terminal as a gate, and a sixth terminal as a source; 
 an output portion that outputs a signal between the second transistor and a second current source to a light emitting element, wherein 
 the first terminal is coupled to a first power source, a signal is input to the second terminal, and the third terminal is grounded through a first current source which is different from the second current source, and 
 the fourth terminal is coupled to a second power source which is the same as or different from the first power source with a second current source, the fifth terminal is coupled to a voltage source or a bias circuit, and the sixth terminal is coupled between the first transistor and the first current source. 
 
     
     
       10. The driving circuit according to  claim 9 ,
 wherein the driving circuit is a single end-type driving circuit. 
 
     
     
       11. The driving circuit according to  claim 9 ,
 wherein the fifth terminal of the second transistor is coupled to the bias circuit that supplies a bias voltage in accordance with a voltage of the first power source. 
 
     
     
       12. The driving circuit according to  claim 11 , further including
 a differential amplifier circuit that differentially amplifies the signal which is input to the second terminal of the first transistor by the first power source at a previous stage relative to the first transistor, 
 wherein the bias circuit generates the bias voltage by adding a positive-phase signal and a negative-phase signal obtained by differential amplification by the differential amplifier circuit. 
 
     
     
       13. The driving circuit according to  claim 9 , further including:
 a differential amplifier circuit that differentially amplifies the signal which is input to the second terminal of the first transistor by the first power source at a previous stage relative to the first transistor; and 
 an extraction circuit that extracts a high-frequency component of a signal obtained by differential amplification by the differential amplifier circuit and supplies the extracted high-frequency component to the fifth terminal of the second transistor. 
 
     
     
       14. The driving circuit according to  claim 13 , further including
 an inductor one terminal of which is coupled to the voltage source or the bias circuit coupled to the fifth terminal of the second transistor and the other terminal of which is coupled to between the extraction circuit and the fifth terminal of the second transistor. 
 
     
     
       15. The driving circuit according to  claim 13 
 wherein a positive-phase signal out of the positive-phase signal and a negative-phase signal obtained by the differential amplification of the differential amplifier circuit is input to the second terminal of the first transistor, and 
 the extraction circuit extracts the high-frequency component from the negative-phase signal.